Chuck



Unitcd States Patent Walter A. Ehrlich, Bridgeport, aml Edward A. Zukowski, Devon, Conn., assignors The Bullard Company, a corporation of Connecticut Application February 9, 1953, Serial N0. 335,736 2 Claims. (C1. 279-119) This invention relates to chucks, and particularly to b that type of chuck in which work is centered by apilo-t prior to gripping.

One 0f the difficulties in proprly holding piloted work on -a chuek during a working operation is the uneven gripping action of the chuck jaws occasioned by sligl1t irregularities o.n the surface of the work. Although prior atternpts have been made to overcome this difiiculty, they have been complieated structures producing substantial frictional forces during operation preventing them from achieving the results desire The prineipal object of this invention is 120 provide a two-jaw -chuck meehanisrn in which equ-alized gripping action of the chuck jaws will be obtained regardless cf slight variations in the gripping surface 0f a workpiece.

Other objects include the provisi-on of a two-jaw chuck,

which jaws are adapted simultaneously to be reciproc-ated toward and from each other in a manner to equalize the gripping pressure of the jaws on a piloted workpiece; the provision 0f such a chuck in which a pivotally mounted yoke element 'i's provided between a draw bar and the chuck actuating levers 0f alwo-jaw chu-ck; and the provision of such a -chuck having a jaw-movement compensating element for insuring equalized gripping pressure from each of the jaws.

The above, other objects and novel features of the invention Will becorne -apparent from the following specification and accompanying drawings, in which:

Figure 1 is a sectional elevational view substantially along line 11 of Fig. 2, showing a =two-iaw chuck 10 which the principles of the invention have been applied; and

Fig. 2 is a top plan view cf the chuck shown in Fig. 1.

Referring to the drawings, and particularly t Fig. l, the invention is shown as applied to a two-jaw chuck in- -clu-ding a base 10 adapted to be fixed to the head 11 0f a w-ork-supporting spindle (only a portion of the head 11 being shown in the drawings). The spindle is rotated in the usual manner by gears attached to its lower end (not shown). A pair of lower jaws 12 and 13 are reciprocably mounted within ways 14 and 15 formed in the base 10. The ways 14 and 15 are formed along a diameter 0f the base 10. The lower jaws 12 and 13 are provided With the usual tapped holes 16 in their upper surfaces for receiving screws adapted adjustably to hold top jaws thereto. The latter are employed to grip the work during a turning operation. A pilot plate is rigidly attached I0 the base 10 by screws 18, and includes a pilot 17, the center 0f Which is coincid nt With the exact cente1 of the chuck base 10. The pilot plate extends into and provides a sliding fit within slots 12 and 13' '0f the lower jaws 12 and 13 t-o prevent chips and foreign matter from affecting the chuck actuating mechanism. Openings 19 Within the pilot plate permit screws to extencl therethrough in =the event it is desired to attach a supplemental pilot to the p'ilotplate for different internal diameter workpieces.

Simultaneous reciprocation of the lower jaws 12 and 2775461 Patented Dec. 25, 1956 "ice 13 toward and from each other is eflected by the -actuation -of hell crank levers 20 and 21 having trunnions 22 and 23 mounted within the base 10. The short arms 24 and 25 of the hell cranks'20 and 21 are spherieal in form and male with corresponding spherical seating members 26 and 27 wi-t-hin the lower jaws 13 and 12, respectively. The free ends of the long arrns 013 the hell craiaks 20 and 21 seat within openings 28 and 29 of a yoke element o: spool 30 pivotally mounted 0x1 a pin '31 that extends across an opening 32 formed Wi'thin a draw bar 33. The comstruction and arrangement of the arts is such that vertical recip1d0ation 0f the draw bar 33 efiects arcuale movemeut ofi the ends of the long arms 0f the bell eranks 20 and 21 to thereby eifeet reeiproca=tive movement of the lower jaws 12 and 13 toward and from each other. -causes the top jaws attached thereto to grip a workpiece mounted on the pilot 17. When the -outer peripheral surface of the workpiece varies slightly, the pivotally mounted yoke element 30 equalizes the action of the gripping jaws mounted 0n the lower jaws 12 and 13 so that equaliz d gripping forces are -applied by the two jaws, thereby efiectively holding the workpiece during a metal working operation.

Although the various features of the improved two-jaw chuck have lasen shown and described in debail t0 fully disclose one embodimenc of the invention, i't will be evident that numerous changes can be made in such detal1s and certain features may be used withou1; others without departing from the principles of the invention.

What is claimed is:

1. In a two jaw chuck, a base; ways Wlthin said base lying along a diameter thereof; jaws in said ways; a Worksupportizig pilot rigidly mounted centr-ally 0f said base; a pivut pin mounted With'in said b ase in a plane including the axis of rotation of said base and -at righ=t angles thereto; a spoon having a groove pivoted on said pin such that the =axis of the pin is diametrical t0 the groove anal Within the plane including said gr-oove; and bell crank levers each having a short and a long arm pivotally mounced within said base With the short arm of each eng'aging one of said jaws, and the long arm of ea'ch engaging said spool Wlll1lll the groove thereof, the length of the long arms being relatively large compared "so the diameter of the spool, whereby a relatively high mechanioal advantage of said hell -cranks oan be obtained.

2. In a two jaw chuck, a base; ways With'in said base lying along a dlameter thereof; jaws Within said ways; a work-supporting pilo't rigidly mounted cen'trally of said base; a draw bar loeated along the longitudinal axis 015 rotation of said base; a pivot pin mounted in an opening extending through said draw bar, said pivot pin intersecting said longitudinal axis at right angles thereto; a spo-ol having a groove pivoted on said pin and lying substantially within the peripheral eonfines 0f said draw bar with said pin lying along a diameter cf said groove and Within a plane including said groove; and bell-crank levers each having long and short arms pivotally mounted within said base with the one end of each short arm engaging one of said jaws, and the en-d of each long arm engaging said spool within the groove thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1539282 Spurr May 26, 1925 17117'87 Hopkins May 7, 1929 2524485 Sloan -1-.. Oct. 3, 1950 2657068 Sl-oan Oct. 27, 1953 FOREIGN PATENTS 404,501 Great Britain Jan. 18, 1934 TlllS action 

